1. Field Of The Invention
The present invention relates to silicon reagents, as well as to a method of forming silicon-containing gate dielectric materials (e.g., silicon dioxide (SiO2), silicates, etc.) and structures using such reagents. Description of the Related Art
Silicon dioxide (SiO2) films doped with early transition metal oxides, e.g., ZrO2 or HfO2, are of great interest for use as next generation gate dielectrics. These silicates provide higher dielectric constants (10-15) than conventional oxide-nitride-oxide stacks. Given the progressively decreasing feature sizes of VLSI devices, chemical vapor deposition (CVD) provides a superior technique for depositing gate dielectric films.
There are several issues associated with CVD of gate dielectrics.
Low temperature CVD silicon precursors are required. Ideally, the silicon precursor decomposes below 600xc2x0 C., forming a silicon oxide film of high purity and high density characteristics.
Additionally, the silicon precursor must be compatible with the dopant reagents that are used to produce doped silicon dioxide films. These dopant reagents include metal (e.g., Zr, Hf, La, Ta, Y, Gd or other transition metal species) xcex2-diketonate complexes such as Zr(thd)2(i-PrO)2.
Capacitors made with the current SiO2 dielectrics are limited in capacitance as the film is made thinner, due to excessive leakage from tunneling. The best candidate higher dielectric constant materials for Si-based CMOS are silicate glasses modified by Zr, Hf, La or Y oxides, since such glasses arc thermally stable in contact with silicon and have a low density of trapped charge at the interface.
Efforts to develop such capacitors have been limited by the absence of suitable precursors from which silicate glasses of such type can be formed.
Traditional precursors such as zirconium isopropoxide can be used to deposit ZrO2, but when a traditional silicon precursor such as silane is added in the process, only a very narrow range of Si:Zr ratios can be grown as oxide glass, and associated gas phase reactions tend to form particles. Even with precursor molecules containing both Si and Zr, the Si:Zr ratio cannot easily be controlled.
The foregoing is complicated by the fact that an upper temperature limit of 650xc2x0 C. is imposed by integration requirements and the objective of limiting thermal oxide growth.
Currently, most silicon precursors either do not decompose at required temperatures, or are not compatible with xcex2-diketonate metal precursors.
Development of new silicon CVD precursors and compositions therefore is desirable.
The present invention relates to novel precursor compositions for low temperature ( less than 600xc2x0 C.) chemical vapor deposition (CVD) formation of silicon-containing films, and to associated methods of making and using such types of compositions.
While encompassing various aspects, as hereinafter more fully disclosed, one aspect of the invention relates to novel hexacoordinated silicon beta-diketonate compositions.
Compositions of such type include those of the formula R2Si(xcex2-diketonate)2 and (RO)2Si (xcex2-diketonate)2, wherein each R is the same as or different from the other R, and each R is independently selected from H, aryl, fluoroaryl, C1-C12 alkyl, and C1-C12 fluoroalkyl.
According to a further aspect, such compositions may be employed to form silicon-containing films of varying types, including doped silicon dioxide films (when a dopant co-precursor is utilized), by chemical vapor deposition (CVD) methodologies.
Yet another aspect of the invention relates to a process for forming a silicate film on a substrate, comprising chemical vapor deposition of the film using as the chemical vapor deposition precursor an alkoxide xcex2-diketonate silicon precursor in combination with at least one of (a) and (b):
(a) an alkoxide xcex2-diketonate precursor for one or more of Zr, Hf, Nb, and Ta, and
(b) a xcex2-diketonate precursor for one or more of Y, La, Sr and Ba.
Another aspect of the invention relates to a chemical vapor deposition precursor comprising an alkoxide xcex2-diketonate silicon precursor in combination with at least one of (a) and (b):
(a) an alkoxide xcex2-diketonate precursor for one or more of Zr, Hf, Nb, and Ta; and
(b) a xcex2-diketonate precursor for one or more of Y, La, Sr and Ba.
Other aspects, features and embodiments of the invention will be more fully apparent from the ensuing disclosure and appended claims.